ᐅ Oiled Douglas fir floorboards are becoming too dark.

Hello everyone,

maybe someone can identify the problem I’m having here. I would appreciate any tips.
I used to have a Douglas fir terrace – everything was great. The wood would darken each year when I applied new oil and gradually turn gray over time.
A few years ago, I had a similar terrace installed at the new house after the WPC decking deteriorated. I suspect it was low-quality material from an outlet sale.
Anyway, the new boards change color year by year. The wood is dark gray and looks almost black when wet.
Only in some corners does the oil treatment work as it should. Those areas are clean. So, it’s hardly the oil’s fault, right?
I read that this could possibly be an iron reaction, but that seems unlikely over such a large area (29 out of 30 square meters (320 square feet)).
I’m attaching a few pictures. I have now cleaned the boards with an electric brush – at least somewhat clean.

What can I do to prevent this from happening again?

Also, a few more pictures, this time showing the dry condition after cleaning. You can see the corners that look as they should and the rest…

Wood is a natural material. It is quite normal for it to weather differently and also react differently to the oil. In my opinion, this is not a defect but simply a characteristic of nature.

Unfortunately, those are “problematic” floorboards with many grooves. I don’t like them because they can’t be easily sanded down like smooth wood. This might not be comforting to you, but otherwise I would have suggested sanding twice (medium and fine grit). However, the issue with the grooves would still remain.

Without having a definite answer, I would like to point out:
This doesn’t look to me like the typical graying or darkening of wood. The stains seem to be distributed independently of the wood grain.
I have no idea if this is really the case or if it helps in any way.
Good luck with your investigation of the cause.

ateliersiegel schrieb:

Without having a clear answer, I just want to point out:
To me, this does not look like the usual greying or darkening of wood. The spots are distributed somewhat independently of the wood grain.
No idea if that's really the case or if it helps at all.
Good luck with figuring out the cause.

Hello,
I believe this is a misunderstanding. What you see in the pictures is the cleaned area. It’s not that simple, as some dark spots are more “stubborn” than others, and I didn’t want to damage the wood completely. In one of the photos, you can see the fully dark beams – that’s before cleaning.
The iron test was negative.
To me, it looks like the oil turned dark in areas where the sun is beating down all day.
I have now cleaned the rest and am switching to oil from a different manufacturer. It’s actually a bit too red for my taste, but okay. Let’s see how it develops.
When I removed the residue with the steam cleaner on the second section, you could see that the top layer – about 0.5mm (0.02 inches) – came off, revealing the natural wood color underneath.
Wood does grey over time, that’s clear – but I had never seen it get this dark before.
A loft bed made from Douglas fir that stands on the terrace still has the same color as when it was first coated, was treated with the same oil, but it was a different type of wood.